Abstract
Background/Aim: Glioblastoma multiforme (GBM) is the most aggressive primary brain tumor, with limited survival despite standard treatments such as surgery, radiotherapy, and chemotherapy. High recurrence rates after gross total resection underline the need for identifying new therapeutic targets. Angiotensin-converting enzyme (ACE) plays a role in angiogenesis and cellular proliferation, making it a potential marker in glioblastoma pathogenesis. This study aimed to evaluate the association between ACE I/D polymorphism and glioblastoma in the Turkish population and explore its potential as a therapeutic target.
Patients and Methods: The study included 35 patients with glioblastoma and 36 healthy controls. DNA was extracted from peripheral blood samples and genotyped using TaqMan SNP Genotyping Assays. Statistical analyses were conducted using IBM SPSS Statistics (v23), with chi-square and Fisher’s exact tests assessing genotype and allele distribution differences. Odds ratios (OR) and 95% confidence intervals (CI) were calculated.
Results: Genotype distribution showed no significant differences between glioblastoma and control groups (p=0.171). However, the D allele was significantly more prevalent in glioblastoma patients (43.7%) than in controls (33.8%) (p=0.027), indicating a fourfold increased risk of glioblastoma (OR=0.258, 95% CI=0.074-0.901). The I allele exhibited a non-significant protective trend.
Conclusion: The D allele of the ACE I/D polymorphism contributes to glioblastoma risk, highlighting ACE as a potential therapeutic target. Further studies are needed to confirm these results and investigate the clinical utility of ACE inhibitors in glioblastoma management.
Introduction
Glioblastoma multiforme (GBM) is the most aggressive and frequently occurring primary brain tumor in adults, characterized by rapid progression, high recurrence rates, and poor prognosis. Despite advancements in neurosurgery, radiotherapy, and chemotherapy, the median survival for GBM patients remains approximately 14-16 months, with a 5-year survival rate below 5% (1-3). The high resistance of GBM to conventional treatments and its invasive nature underscore the urgent need for novel therapeutic approaches and molecular targets.
In recent years, significant attention has been directed toward understanding the molecular underpinnings of GBM pathogenesis. Among these, the renin-angiotensin system (RAS), traditionally known for its role in cardiovascular homeostasis, has emerged as a key player in cancer biology. Angiotensin-converting enzyme (ACE), a zinc metallopeptidase, is a critical component of RAS, facilitating the conversion of angiotensin I to the pro-angiogenic angiotensin II while degrading vasodilatory peptides such as bradykinin. Dysregulation of ACE has been implicated in several cancers, including gliomas, through its influence on angiogenesis, cellular proliferation, and inflammation (4-7).
ACE gene polymorphisms, particularly the insertion/deletion (I/D) polymorphism in intron 16, have been associated with altered serum ACE levels. The DD genotype is linked to the highest ACE levels, followed by the ID and II genotypes (7). Several studies have reported correlations between the ACE I/D polymorphism and the risk of cancers such as lung, prostate, and pancreatic cancers, with varying results across populations (6, 8-11). Emerging evidence suggests a potential link between the D allele and increased glioblastoma risk, possibly due to enhanced angiogenesis and tumor invasiveness driven by elevated ACE activity (5, 12, 13).
Given the limited number of studies exploring this relationship, particularly in the Turkish population, this study aimed to investigate the association between ACE I/D polymorphism and glioblastoma. By examining genotype and allele distributions in glioblastoma patients and healthy controls, we aimed to elucidate the potential role of ACE as a biomarker and therapeutic target in GBM. Understanding these molecular mechanisms could contribute to the development of more effective, targeted treatment strategies for glioblastoma.
Patients and Methods
Study design and population. This case-control study was conducted to evaluate the association between the ACE I/D polymorphism and glioblastoma in the Turkish population. The study included 35 patients diagnosed with glioblastoma and 36 healthy controls without any history of malignancy. Ethical approval for the study was obtained from the Marmara University Clinical Research Ethics Committee (Approval Number: 09.2022.592/01.04.2022). Written informed consent was obtained from all participants.
Sample collection and DNA extraction. Peripheral blood samples (350 μl) were collected in EDTA tubes from all participants. DNA was isolated using the iPrep PureLink gDNA Blood Isolation Kit (Invitrogen, Life Technologies; Thermo Fisher Scientific Inc., Waltham, MA, USA) according to the manufacturer’s instructions. The extracted DNA was stored at 4°C until further analysis.
Genotyping of ACE I/D polymorphism. ACE I/D polymorphism genotyping was performed using TaqMan SNP Genotyping Assays (Catalog number: 4351379, SNP ID: rs1799752, Thermo Fisher Scientific Inc., Waltham, MA, USA) on a 7500 Fast Real-Time PCR System (Applied Biosystems, Foster City, CA, USA). The assay included three primers and two allele-specific probes: The primer sequences were: ACE111: 5′-CCC-ATC-CTT-TCT-CCC-ATT-TCT-C-3′; ACE112: 5′-AGC-TGG-AAT-AAA-ATT-GGC-GAA-AC-3′; ACE113: 5′-CCT-CCC-AAA-GTG-CTG-GGA-TTA-3′. The probes used were: I allele-specific probe: VIC-5′-AGG-CGT-GAT-ACA-GTC-A-3′-MGB; D allele-specific probe: FAM-5′-TGC-TGC-CTA-TAC-AGT-CA-3′-MGB.
The PCR amplification mixture consisted of 10-50 ng of genomic DNA and TaqMan Genotyping Master Mix (Catalog number: 4371353, Thermo Fisher Scientific Inc.). Amplification cycles included an initial denaturation at 92°C for 15 s, followed by 40 cycles of annealing and extension at 57°C for 1 min. The results were analyzed using SDS Plate Utility v2.2 software (Applied Biosystems).
Statistical analysis. All statistical analyses were conducted using IBM SPSS Statistics v23 (IBM Corp., Armonk, NY, USA). The chi-square test and Fisher’s exact test were used to compare the genotype and allele frequencies between glioblastoma patients and controls. Student’s t-test and chi-square tests were used to compare demographic variables. Odds ratios (OR) and 95% confidence intervals (CI) were calculated to estimate the risk of glioblastoma associated with ACE genotypes and alleles. A p-value <0.05 was considered statistically significant.
Results
Participant characteristics. The study included 35 glioblastoma patients and 36 healthy controls. There were no significant differences between the groups in terms of demographic variables, including age and sex (p>0.05).
Genotype distribution. The distribution of ACE genotypes in glioblastoma patients and healthy controls is shown in Table I. The II genotype was observed in 8.6% of glioblastoma patients and 22.2% of controls. The ID genotype was observed in 54.3% of glioblastoma patients and 36.1% of controls. The DD genotype was observed in 37.1% of glioblastoma patients and 41.7% of controls. No statistically significant difference was found between the groups in genotype distribution (χ2=3.527, p=0.171).
The distribution of the ACE genotypes in the study groups.
Allele frequencies. The allele frequencies of ACE I/D polymorphism are shown in Table II. The D allele was significantly more frequent in glioblastoma patients (43.7%) compared to controls (33.8%) (p=0.027). The I allele frequency was higher in controls (29.6%) than in glioblastoma patients (18.3%), but this difference was not statistically significant (p=0.697).
Allele frequencies of the ACE I/D polymorphism in the study groups.
Risk analysis. The D allele was associated with an approximately fourfold increased risk of glioblastoma (OR=0.258, 95% CI=0.074-0.901, p=0.027). The I allele showed a trend toward a protective effect but was not statistically significant (OR=0.827, 95% CI=0.319-2.147, p=0.697).
The frequency of individuals carrying the I allele was 18.3% (n=13) in the patient group and 29.6% (n=15) in the control group; however, no statistically significant difference was observed between the groups (p=0.697). In contrast, the proportion of individuals carrying the D allele was significantly higher in the patient group (43.7%, n=31) compared with the control group (33.8%, n=24), and this difference reached statistical significance (p=0.027).
Risk analysis based on these findings demonstrated a significant association between ACE deletion polymorphism and glioma susceptibility (OR=0.258, 95% CI=0.074-0.901). The higher prevalence of the D allele non-carriers in the control group suggests that absence of the ACE D allele may exert a protective effect against glioma development
Discussion
GBM is a highly aggressive primary brain tumor with limited treatment options and poor prognosis, highlighting the urgent need for novel therapeutic approaches. This study investigated the association between ACE I/D polymorphism and glioblastoma in the Turkish population, providing insights into the potential role of ACE as a molecular marker and therapeutic target. The findings revealed that while the distribution of ACE genotypes did not significantly differ between glioblastoma patients and controls, the D allele was significantly more prevalent in the glioblastoma group, suggesting its role in glioblastoma pathogenesis (5, 12).
The observed association between the D allele and glioblastoma aligns with previous studies demonstrating that elevated ACE levels promote tumor progression by enhancing angiogenesis, inflammation, and cellular proliferation (5, 7, 9). Angiotensin II, the primary effector molecule of ACE, has been shown to upregulate vascular endothelial growth factor (VEGF) expression and stimulate neovascularization, which are critical for glioblastoma growth and invasion (6, 7). Conversely, the I allele, associated with lower ACE activity, exhibited a trend toward a protective effect in this study, potentially due to reduced levels of angiotensin II and its downstream effects on tumorigenesis. While not statistically significant, this observation supports the hypothesis that genetic variations influencing the renin-angiotensin system (RAS) may modulate glioblastoma risk and tumor behavior (9, 12).
Study limitations. Despite these findings, the study has limitations that must be considered when interpreting the results. The relatively small sample size may have limited the statistical power to detect subtle differences in genotype and allele distributions between groups, and the findings may not be generalizable to other populations due to potential ethnic variability in ACE polymorphism frequencies. Additionally, the study focused solely on the association between ACE polymorphism and glioblastoma risk without examining its impact on survival, treatment response, or disease progression. Such data would provide valuable insights into the clinical utility of ACE as a biomarker. Furthermore, environmental and lifestyle factors, which may interact with genetic predispositions to influence glioblastoma development, were not assessed.
The clinical implications of these findings warrant further investigation. ACE inhibitors (ACEi) and angiotensin receptor blockers (ARB), which are widely used in cardiovascular disease management, have demonstrated anti-tumor effects in preclinical models, including inhibition of angiogenesis and tumor proliferation (12, 13). These agents may represent promising adjuvant therapies in glioblastoma management, potentially improving outcomes when combined with standard treatments. However, conflicting results in the literature regarding their efficacy in glioblastoma underscore the need for robust clinical trials to evaluate their therapeutic potential and safety profiles in this context.
Integrating comprehensive genomic, molecular, and environmental analyses could provide a more nuanced understanding of glioblastoma pathogenesis and the interplay between genetic and non-genetic factors (4, 14, 15). Additionally, clinical trials investigating the role of ACEi and ARB in glioblastoma treatment are essential to validate their potential utility and establish evidence-based recommendations.
In conclusion, this study highlights the potential role of the ACE D allele in glioblastoma risk and reinforces the importance of the RAS in tumor biology. While these findings contribute to the growing body of evidence on the molecular mechanisms underlying glioblastoma, further research is essential to translate these insights into effective therapeutic strategies. By expanding our understanding of genetic polymorphisms and their impact on glioblastoma, we can move closer to developing targeted, personalized treatments for this devastating disease.
Conclusion
This study identifies the ACE D allele as a potential risk factor for glioblastoma, emphasizing the role of the renin-angiotensin system in tumor progression. While the findings suggest therapeutic potential for ACE inhibitors, further research is needed to confirm these results and explore their clinical applications in glioblastoma management.
Footnotes
Authors’ Contributions
Okan Türk: Corresponding author, organized and coordinated the research. Yahya Güvenç: Supervised the study. Seda Güleç Yılmaz: Carried out the laboratory work and data analysis. Cumhur Kaan Yaltirik: Led the article writing. Adnan Dağçınar, Turgay İsbir: Contributed to the study design. Nail Demirel, Ömer Faruk Şahini, Oğuz Alp Çakır, Nafite Şanlıer, Ufuk Emre Toprak, Muhammed Teoman Kurt: Assisted in sample and data collection.
Conflicts of Interest
The Authors declare no conflicts of interest related to this study.
Artificial Intelligence (AI) Disclosure
During the preparation of this manuscript, a large language model (ChatGPT, OpenAI) was used solely for language editing and stylistic improvements in select paragraphs. No sections involving the generation, analysis, or interpretation of research data were produced by generative AI. All scientific content was created and verified by the authors. Furthermore, no figures or visual data were generated or modified using generative AI or machine learning-based image enhancement tools.
- Received January 12, 2026.
- Revision received February 12, 2026.
- Accepted February 18, 2026.
- Copyright © 2026 The Author(s). Published by the International Institute of Anticancer Research.
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
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